CMPWR280 데이터 시트보기 (PDF) - California Micro Devices => Onsemi

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CMPWR280

1.5A SmartOR™ Dual Regulator with VAUX Drive

California Micro Devices => Onsemi 

CALIFORNIA MICRO DEVICES

CMPWR280

Interface Signals

VCC is the primary 5V power supply for the internal regulator.

Whenever VCC exceeds VCCSEL (4.5V), the internal regulator

(1500mA) will be enabled and deliver a fixed 3.3V at VOUT.

When VCC falls below VCCDES (4.1V typically) the regulator

will be disabled.

Internal loading on this pin is typically 1.5mA when the

regulator is enabled, which reduces to 0.2mA whenever

the regulator is disabled. If VCC falls below either the VSBY or

VOUT voltage, the loading on VCC will reduce to only a few

microamperes.

During a VCC power up sequence, there will be an effective

step increase in VCC line current when the regulator is enabled.

The amplitude of this step increase will depend on the dc

load current and any current required for charging/

discharging the load capacitance. This line current transient

will cause a voltage disturbance at the VCC pin proportional

to the effective power supply source impedance being

delivered to the VCC input.

To prevent chatter during Select and Deselect transitions, a

built-in hysteresis voltage of 400mV has been incorporated.

It is recommended that the power supply connected to the

VCC input should have a source impedance of less than 0.15Ω

to minimize the chatter during the enabling/disabling of

the regulator.

VSBY is the standby 5V supply power source, which is only

selected on when VCC < VCCDES. If VSBY is selected, the

regulator can deliver a maximum of 375mA load current.

Whenever VSBY exceeds both VCC and VOUT, it will be used to

provide all the internal bias currents and any necessary

regulator current.

GND is the reference for all voltages. The current that flows

in the ground connection is very low (typically 2.0mA) and

has minimal variation over all load conditions

VOUT is the regulator output voltage connection used to power

the load. An output capacitor of ten microfarads is used to

provide the necessary phase compensation, thereby preventing

oscillation. This capacitor also helps to minimize the peak

output disturbance during power supply changeover.

When both VCC and VSBY fall below VOUT, VOUT will be used to

provide the necessary quiescent current for the internal

reference circuits. This ensures excellent start-up characteristics

for the regulator.

Drive is an active LOW logic output intended to be used as

the control signal for driving an external P-channel MOSFET

switch whenever the regulator is disabled. This will allow the

voltage at VOUT to be powered from an auxiliary supply voltage

(3.3V).

The Drive pin is pulled HIGH to VCC whenever the regulator is

enabled, thus ensuring that the auxiliary supply remains isolated

during normal regulator operation.

Symbol

VSBY

VCC

GND

VOUT

Drive

Pin Functions

Description

Standby Positive 5V Supply input. Used to power internal regulator (375mA) when VCC is not

available.

Main Positive 5V Supply input. Powers the internal regulator (1.5A) whenever VCC exceeds the select

threshold (typically 4.5V)

Ground Reference for all voltages.

Regulator output voltage (3.3V).

Logic signal for controlling external auxiliary switch. Active LOW output whenever the internal

regulator is disabled.

© 2000 Calirornia Micro Devices Corp. All rights reserved.

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215 Topaz Street, Milpitas, California 95035 Tel: (408) 263-3214 Fax: (408) 263-7846 www.calmicro.com

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